This trope is Emotions Versus Stoicism given character form. The Rash Foil is emotional, and the Calm Foil is stoic. This gives them a specific set of differing personalities, and with it, very different approaches to the world in general. It also mans they always have something to butt heads about, since their manner of acting may rub each other the wrong way and each is sure that their side of the spectrum is right. Their personalities usually run roughly along the following lines: The Rash Foil is associated with passion, wildness, and defiance. A rash character is often more brawny than brainy, more emotional than contemplative, more social than introspective, more impulsive than scheming, and filled with a zest for life. He is also much more likely to break conventions and rules than his twin. Often an Idiot Hero or a Boisterous Bruiser. Does not have to be stupid, but are much more emotional than the Calm Foil, and tend to express themselves more simply. Villainous versions are often a Blood Knight. A Rash Foil is most likely The McCoy. The Calm Foil has a preponderance of traits diametrically opposed to the Rash Foil. A calm character is more intellectual than combative, prefers contemplation to excitement, derives pleasure from introspection more than socialization, spends time predicting before enacting, and take great pride in their abilities. He possesses a greater respect for traditions and legal methods when compared to his counterpart. Often a Guile Hero, or a Chess Master. Physical inability to complete menial labor is not required, but are much more controlled, making some of them wound far too tight beneath their calm and unemotional appearance. Villainous versions are often a Clock King, or Manipulative Bastard. A Calm Foil is most likely The Spock. There are a lot of ways to play their interactions; Both can be lead characters, or one can be the main character with the other one picking up The Lancer. Sometimes both are supporting for the main hero. They may also play off of Order Versus Chaos, with Rash Foil taking Chaos, and Calm Foil taking Order. In a show where it's relevant, differences in fighting style may be something like Technician vs. Performer. For example, a Rash Foil may rush headlong into melee combat without focus or a plan, while the Calm Foil may use cunning traps and strategies, attempt Single-Stroke Battle, or rely on hitting a target with ranged attacks from a distance instead of running up to their opponent and punching them in the face. For more on this, read Cast Calculus. Subtrope of Odd Couple. Compare Outside Man, Inside Man, Tomboy and Girly Girl, and Sensitive Guy and Manly Man. When this trope is used with Eastern symbolisms, you may have a Tiger Versus Dragon pairing, with the Tiger (reckless) and the Dragon (patient). When this trope is color coded with the colors red (rash) and blue (logical), that's Red Oni, Blue Oni.
Hello, Unknown Troper. You'll need to get known to lend a hand here.